The overall goal of this SCCOR proposal is to elucidate the roles of innate and adaptive immunity in the pathogenesis of chronic lung disease. The SCCOR proposal consists of four interrelated research projects that are focused on two chronic lung diseases: asthma and bronchiolitis obliterans syndrome (BOS) with a common underlying theme of epithelial injury, inflammation, repair and fibroproliferation. The central hypothesis to be tested is that chronic lung disease occurs as a consequence of destructive or maladaptive host responses to common environmental insults that challenge the lung. The fundamental roles of innate and adaptive host responses are to recognize invading antigens, pathogens or altered self components with the purpose of eradicating the offending agents and restoring tissue integrity. While resolution can occur when the host response is normal, an exogenous insult cannot be contained when a critical host factor is inactivated, dysregulated, or becomes dysfunctional. Such maladaptive host responses lead to chronic lung disease. The project specific hypotheses within this SCCOR proposal are: Project 1: Surfactant proteins SP-A and SP-D, which are produced by both alveolar and airway cells, interact with cells of both the adaptive and innate immune systems to coordinately maximize defense against inhaled allergens and that cause and exacerbate asthma, while minimizing an over exuberant immune response that could result in inflammation, tissue damage and chronic lung disease. Project 2: Interleukin 13 (IL-13) modulates airway fibroblast function in human asthma via increased expression of platelet-derived growth factor (PDGF), an adaptive host response, and subsequent airway remodeling via fibroblast proliferation, collagen expression and decreased elastin expression. Project 3: Activation of innate immunity through toll like receptors (TLRs) in the transplanted lung promotes the adaptive alloimmune response leading to acute rejection and BOS. Project 4: Innate immune mechanisms regulate chronic inflammation and tissue remodeling and specifically, host hyaluronan and TLR interactions are critical components of the injury and repair response in non-infectious lung injury, BOS and chronic asthma. These studies will contribute to our understanding of normal and altered host responses on lung structure and function and will provide a basis for investigation and development of new therapies for the treatment of chronic lung diseases. (End of Abstract) INDIVIDUAL PROJECTS AND CORE UNITS PROJECT 1. Immunoprotective Effects of Surfactant Proteins in Asthma (Wright, Jo R.) DESCRIPTION (provided by applicant): Although pulmonary surfactant has been traditionally viewed as a surface tension reducing substance, recent studies demonstrate that it also functions in host defense. Two surfactant proteins, SP-A and SP-D, are members of a family of innate immune proteins known as collectins that bind pathogens and facilitate their clearance by immune cells. SP-A and SP-D also regulate a variety of immune cell functions. The overall hypothesis to be tested in this proposal is that SP-A and SP-D. which are synthesized and secreted by both alveolar and airway cells, interact with cells of both the adaptive and innate immune systems to coordinatelv maximize defense against inhaled allergens that cause and exacerbate asthma, while minimizing an over exuberant immune response that could result in persistent inflammation, tissue damage and chronic lung disease. We propose to evaluate the roles of SP-A and SP-D in regulating functions of two immune cells that play a role in asthma pathogenesis: dendritic cells and T-lymphocytes. Preliminary studies show that SP-D enhances antigen uptake and presentation by dendritic cells, that SP-A and SP-D inhibit lymphocyte proliferation, modulate production of regulatory and inflammatory cvtokines by dendritic cells and that SP-A null mice have enhanced susceptibility to lung injury and allergic inflammation. Our hypothesis is also supported by published studies showing that SP-A and SP-D inhibit allergen-induced lymphocyte proliferation and histamine release by immune cells from asthmatic children and by studies showing that SP-D null mice are more susceptible to allergic inflammation. Four aims are proposed. Aim 1 will determine the mechanisms by which SP-A and SP-D and their receptors, including toll like receptors (TLRs), regulate dendritic cell function. Studies will be conducted in vitro with isolated cells and in vivo with mice. Aim 2 will investigate the mechanism by which SP-A and SP-D regulate lymphocyte activation and whether SP-A and SP-D directly or indirectly (via dendritic cells) affect T-cell proliferation and polarization to a TH1 or Tn2 phenotype. Aim 3 is to investigate the role of SP-A and SP-D in the pathogenesis of inflammatory lung disease using mouse models of asthma and chronic allergic inflammation in collectin null mice. Aim 4 is to compare characterize levels of SP-A and SP-D in lavage fluid from asthmatics and normals. These studies will provide information about the role of SP-A and SP-D in regulating the functions of two important cells of the adaptive immune system and contribute to our understanding of the role of SPA and SP-D inflammatory lung diseases. This project investigates the role of TLRs in chronic lung disease in conjunction with Projects 2, 3 and 4. In addition, patient samples from Project 2 will be analyzed. The project will interact with all the Cores. (End of Abstract)